Clamp



Oct. 28, 1941. R. F. HINCl-[MAN CLAMP Filed May 2'7, 1940 Patented Oct. 28, 1941 UNITED STATE CLAMP Ralph F. Hinchman, Aurora, 111., .assignor to All Steel-Equip Company, Aurora, Ill.,,a corporation of Illinois Application May 27, 1940; Serial No.'337,396 2 Claims. 01. ass-24.5)

This invention relates to clamps in general and particularly to clamps for use in connection with switch boxes, outlet boxes and other electric receptacles. More specifically, the invention relates to a clamp or clamping member for clamping non-metallic cable to an electric receptacle.

An important object of the inventionyis, the provisionpf a one piece integral cable clamp stamped or cut from a single piece of sheet metal material and formed or configurated to provide a clamping member adapted to be arranged or positioned in an electric receptacle to permit clamping engagement of a non-metallic cable whether the cable enter the receptacle from a side or the bottom, the clamp also being provided with means to bush the cable sheath away from the sharp edges of the knockout opening.

Another important object of the invention resides in the provision of a clamp which is held clear of the knockout until actually needed; which permits the cable to enter through the side or end knockouts or through the bottom; which accommodates a wide range of sizes, and which can be quickly and conveniently brought. to clamping engagement by the mere manipulation of a single fastening screw.

Another object is the method of making a one piece clamp from a single pre-cut blank by bending the blank along certain predetermined lines to provide opposed clamping surfaces integrally connected together by strips, and then bending the strips to permit collapsibility thereof.

A further object of the invention is the pro-.

vision of a one piece resilient clamping member,

which. is strong and durable in construction, which is elficient and positive in operation, which can-be readily and economically manufactured, which may easily and quickly be installed and applied, and which is not likely to get out of order. 7

Numerous other objects and advantages will be apparent throughout the progress oi-thefollowing specification. 1

The accompanying drawing illustrates a certain selected embodiment of the invention and the views therein are as follows: 7

Fig. 1 is a detail or fragmentaryview of an electric switch box and embodying the invention;

Fig. 2 is a detail vertical sectional view thereof; Fig. 3 is a detail sectional view on the line 3-.3 of Fig. 2; Fig. 4 is a detail plan view of the one piece blank from which the clamp is formed; and

perse.

The particular construction herein shown for the purpose of illustrating. the invention comprises a conventional electric receptacle in the form of a switch box 6 having a bottom I to which the end walls 8, Sam integrally connected. Side walls 29, 9 are detach-ably connected to the end walls 8 in any conventional manner. The-box 6 is provided with knockouts l0 placed at desirable pre-selected locations in the side walls, end walls and bottom. Cables H, comprising the insulated conductors 12, I2, and the outer sheaths'l3 therefor are adapted to pass through openings provided in the box when knockouts are removed, so that the proper electric connectionmay be made within the box 6.

Non-metallic cable has come to be in great demand and considerable amounts of this type of material have been used with success, replacing the conventional conduit and BX cable. This non-metallic cable herein designated by the numeral II includes the usual insulated conductors l2 and the outer non-metallic sheath l3. In the use of non-metallic cable great care must be exercised to prevent the cable clamps themselves from cutting through the insulation or the clamp from pressing the cable too tightly against the sharp edges of the material surrounding the knockout opening. In either instance the clamp and opening must be such as to prevent cutting .o f-the cable so as not to cause a short circuit of thelconductors. Means therefore, must be provided to prevent mutilation of the cable in any ,way: Moreover it is desirable that a clamp be provided which is susceptible of assuming various positions in the box to effect proper and multiple usage. v The present invention not only supplies all the features desired, but further overcomes all the disadvantages which are inherent to conventional structures and constructions. The presentinvention accomplishes the desirable features and overcomes the undesirable features by the pro- Vision of aclamp M which is practically universal inits application and insures proper clamping actionwithout mutilation of the cable. The clamp i4 is preferably stamped from a flat sheet of metalin the form of a blank l5 having openings, cut-outs or-slits l6 and formed therein-as shown in Fig. 4. The blank i5 is bentto the proper and desired, configuration as shown in Fig. 5.. The clamp M has'an upper clamping part [8 and an upwardly extending flange [9, the parts Fig. 5 is a detail perspective view of the clamp more cables I3 pass through from the bottom of the box 6. The top I8 and the bottom 25 are connected together by the side connecting members or pieces 26 which are bent inwardly in the form of a V as indicated at 21, Fig. 5, whereby a certain amount of resiliency is provided as well as collapsibility whereby the top and bottom may be drawn toward each other when the fastening means 24 is tightened.

The front end of the bottom 25 is turned over as indicated at 28 to provide a rounded smooth bearing for the cable, the same being formed from the part 29 of the blank I5. The rear edge of the bottom 25 is likewise formed with a rolled edge 30 of a height slightly higher than the distance from the bottom of the box 6 and the lower edge of a knockout opening so that all clamping action by the fastening member will be between the top I8 and the rolled edges 28 and 30 and not with the sharp jagged edge at the knockout opening. The rolled edge 38 is turned from the part 3| of the blank I5 which also has cutouts 32 formed therein so as to provide an opening or recess when rolled, to let the screw 24 pass unhampered. For convenience the rolled edge 28 may be slightly higher than the edge 30 as shown, or both may be the same height.

The clamp I4 is adapted to be interchanged in the box in any convenient location, that is, the clamp may have its bottom resting on the bottom, a side, or end wall of the box as desired, depending upon the manner in which the cables are to be led into the box. The clamp I4 is adapted to clamp the cables even though they come from different directions as shown in Fig. 1. In this latter figure, one cable enters the box from the bottom, while another enters from the end. The clamp always is completely clear of the knockouts, and permits the cables to be put into place readily and easily.

In operation the clamp I4 is positioned in a corner of the box, the clamp being held in place by the screw 24 threadedly engaging a threaded opening formed in the box for this purpose. After one or more knockouts are removed the non-metallic cable is led through the openings to the inside of the box. As they pass through the knockout openings they are positioned between the top I8 and the bottom 25 of the clamp. After so positioned, the fastening means 24 is tightened to drawn down the top towards the bottom, a feat which is readily accomplished because of the flexibility of the side members 26. The clamp I4 is thus locked to the box, and the cable is securely locked in position by the pressure of the top I8 against the cables which lie between the top I8 and the bottom 25. The clamp I4 is also readily able to be positioned in place because of the guiding action of the flange I9 which is adapted to engage an enclosing wall of the box. The tightening of the fastening means 24 securely locks the cable or cables between the upper and lower surfaces of the clamp,

with the cables positioned in the dished or concave surfaces 22 of the upper surface and lying firmly on the smooth rolled-over edges 28 and 30 on the bottom. The cable, therefore, rests against the smooth round edges 28, 30 of the clamp and is prevented from becoming out or otherwise mutilated by any sharp edges which may surround the knockout opening.

The invention provides a clamping member which permits side, end or bottom entrance of the cables through the box, or both simultaneously. Moreover, the smooth rounded edges 28 and 30 bush the cable sheath away from the sharp edges about the knockout opening. The clamp is also of suflicient capacity to accommodate various sizes of non-metallic cable, as well as being held clear of the knockout until it is ready to be used. Regardless of the directions in which the cables I3 lead to the box, they may be securely looked in place by a single, one piece, flexible metal clamp.

Changes may be made in the form, construction and arrangement of the parts without departing from the spirit of the invention or sacrificing any of its advantages, and the right is hereby reserved to make all such changes as fairly fall within the scope of the following claims.

The invention is hereby claimed as follows:

1. A one piece clamping member stamped from a single piece of flat sheet metal and configurated to provide a pair of opposed spaced apart clamping surfaces to receive clampingly therebetween a cable or conduit, one of said surfaces being shaped to conform with a surface 1 of a cable, the other of said surfaces being provided with an opening therein through which a cable may pass, said latter surface being provided with rolled ends on opposite edges thereof to support a cable, said ends being higher than the distance between an edge of a knockout in an outlet box with which the clamping member is used whereby to eliminate the cable contacting the sharp edges of the opening formed by the removal of a knockout, and metal strips integral with the said surfaces to maintain the said surfaces in predetermined spaced relationship.

2. A one piece clamping member stamped from a single piece of flat sheet metal and conflgurated to provide a pair of opposed spaced apart clamping surfaces to receive clampingly therebetween a cable or conduit, one of said surfaces being shaped to conform with a surface of a cable, the other of said surfaces being provided with an opening therein through which a cable may pass, said latter surface being provided with rolled ends on opposite edges thereof to support a cable, said ends being higher than the distance between an edge of a knockout in an outlet box with which the clamping member is used whereby to eliminate the cable contacting the sharp edges of the opening formed by the removal of a knockout, metal strips integral with the said surfaces to maintain the said surfaces in predetermined spaced relationship, said strips being relatively resilient to permit the surfaces to be drawn together, and a fastening member passing through one of said surfaces and engageable with the outlet box to draw the said surfaces together to clamp a cable between at least one of said rolled ends on one surface and the other surface. I

RALPH F. HINCHMAN. 

